Dr. Lester is interested in the regulation of insulin secretion from pancreatic beta (B) cells. Regulation of insulin secretion is disturbed in non-insulin dependent diabetes mellitus (NIDDM) by unknown mechanisms. Better understanding of the regulation of insulin secretion and determination of ways to modify insulin release would help in the treatment of patients with NIDDM. In this proposal, Dr. Lester describes a novel mechanism for the control of insulin secretion. Recently, an anchoring protein known to bind protein kinase A (PKA), called AKAP 79, was found to bind the calcium/ calmodulin dependent phosphatase calcineurin (CaN). PKA modulates insulin release by phosphorylating and activating key B-cell proteins such as the voltage-gated L-type Ca 2+ channel. Activation of the channel results in elevations in intracellular calcium concentrations that subsequently activate calcium dependent enzymes like CaN. CaN deactivates proteins such as the L-type Ca 2+ channel by dephosphorylation. Dr. Lester proposes that PKA and CaN are co-localized, through their interaction with AKAP 79, near key proteins such as the L-type Ca 2+ channel. This co-localization may be required for feedback regulation of insulin secretion. To evaluate this hypothesis she plans to: 1) demonstrate the co-localization of CaN, PKA and AKAP 79 in pancreatic B-cells, 2) determine the targeting domain for AKAP 79 in B- cells, 3) synthesize a peptide which inhibits binding of AKAP 79 to its targeting domain and 4) evaluate the effect of disrupting localization of CaN, PKA and the CaN/PKA/AKAP 79 complex using inhibitory peptides on changes in phosphoprotein mapping and insulin secretion from pancreatic B- cells.